I cannot comment on H&Rs, but I had an 83 528e and now have an '87 535is,

I thought the 528e quite capable-some lean, but very tossable, but the 535is springs and (I understand Sport Bilsteins) are a nice combination for more spirited driving.

They are firm, but not harsh, and control the car without any bad characteristics. I recommend the combination. Best of all they should be obtainable right at the dealer or after market parts supplier.